As far as I know, just a few steps are necessary to reproduce this issue:
1. Setup a simple smb server on machine a, like the one I've attached to this
report.
2. Create a smb user on machine a: smbpasswd -a $username
3. Enable smb in auto.master on machine b (and set the timeout to something
small, e.g., 30 secs):
/media/smb/ program:/etc/auto.smb
4. Save the credentials on machine b: echo
"username=$username\npassword=$password" > /etc/creds/machineb
5. Try to access the home directory from machine b:
user@machineb:~$ ls -lh /media/smb/machineb/$username
6. The smb mount is still there after more than 30 seconds